Page 132 - Land Snails of New Mexico

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SpeciestakenateachelevationareindicatedinTable3, except for the slug Deroceras laeve, which was observed at severalstations,butwasnotcollected.Numberofspecimens, perspecies, collected at each locality is indicated, except where voucher specimens, only, were collected in cases indicated by
atslightlylowerelevationsintheSB transect.Inallcases,these species were taken as low as 6,800ft in the S B transect, but only down to7,200or7,500ftintheSacM transects.Thislikely relates to Three Rivers Canyon being somewhat narrower and supporting a more mesic arboreal flora to lower elevations than isthecaseinPeñascoandTularosaCanyons.Thesespeciesare Microphysula ingersolli, Pupilla blandi, Radiodiscus millecostatus, Striatura meridionalis, Vallonia cyclophorella, and Vertigo modesta.
"X." Forthetwotransects,combined,36speciesweretaken. Thirty-threespeciesweretakenalongthePCtransect,with19 in the P C F and 32 in the P C V habitats. Twenty-nine species were taken along the T C transect (these totals include Deroceras laeve). Six species were collected along P C only: Gastrocopta quadridens, Helicodiscus eigenmanni, Paralaoma caputspinulae, Pupoides albilabris, Radiodiscus millecostatus,
In contrast to the above species, Ashmunella rhyssa and Pupilla sonorana were taken at lower elevations in the S a c M transects (5,700 and 6,000 ft, respectively) than in the S B transect(6,800ftforboth).Pupillasonoranaalsoextendsto higherelevationsintheSacMtransects(9,600ft)thanintheSB (8,000ft)transect,andthissuggeststhatitmay preferhabitats
andVertigoelation.ThreespeciesweretakenalongTC only: Carychium exiguum, Gastrocopta ashmuni, and Oxyloma retuSum.
Along the Sacramento Mountains transects, 12 species were taken, which were not recorded for the Sierra Blanca transect:
available in the Sacramento Mountains. A similar pattern is exhibitedby Valloniaperspectiva,which extendsmuch higher (9,300ft)intheSacM thanintheSB (6,800ft)transect.
Carychium exiguum, Gastrocopta armifera, G. ashmuni, G. contracta,G. procera, Oxyloma retusum, Pupoides albilabris, Rabdotus dealbatus neomexicanus, Succinea sp., Vallonia gracilicosta, V. parvula, and Vertigo elatior. Only 3 species were found in the SB, but not in the PC or TC transects: Columella columella, Oreohelix nogalensis, and Pupilla muscorum. Although the Sacramento Mountains transects c u l m i n a t e d a t e l e v a t i o n s s o m e 2 , 2 8 0 ft ( P C ) a n d 3 , 4 8 0 ft ( T C ) lowerthantheSBtransect,thenumberofspeciesfoundis greater. It seems likely that the widespread presence of calcareous bedrock in the Sacramento Mountains area produces c o n d i t i o n s s u p p o r t i v e o f a m o r e d i v e r s e f a u n a . It is, o f c o u r s e ,
ParalaomacaputspinulaewasacommonsnailintheSB t r a n s e c t , t a k e n f r o m 6 , 8 0 0 t o 1 0 , 4 0 0 ft, b u t w a s f o u n d a t o n l y o n e l o c a l i t y i n t h e S a c M t r a n s e c t s , a t 8 , 4 0 0 ft. T h i s s u g g e s t s t h a t its preferences, regarding the habitats offered by the two mountain ranges involved, contrast with those of the species discussed in the preceding paragraph.
well documented that some species of land snails are more
Maximum densities (total specimens) occur within the generalrange of7,200-9,300 ft(maximal numbers are at7,500 and 8,700 ft). This is similar to the altitudinal pattern of specimendensitiesforSB localities(Table2)wherethethree largestnumbersofspecimenswereat8,000,8,400,and 10,400 ft. T h e S a c r a m e n t o M o u n t a i n s t r a n s e c t s r e a c h e d o n l y t o 9 , 6 0 0 ft, w i t h c a n y o n h a b i t a t p r o g r e s s i v e l y d i m i n i s h i n g , u p w a r d , o n t h e widespread, relatively level crest of the range. Thus, habitats
calciphilic than others. Rabdotus dealbatus neomexicanus is
such a calciphilic species. Four species of Gastrocopta, which
wererecordedfromtheSacramentoMountains,werenotfound alongtheuppermostSacramentoMountainstransectsdiffer
in any of the four transects on igneous bedrock. Perhaps s o m e of these are also calciphiles.
significantly from those at comparable elevations along the S B
The three species found in the Sierra Blanca Mountains, but not in the Sacramento Mountains, m a y find the higher elevations availableintheSB transectmorefavorable.Perhapstheyare relicts there. This is suggested because Oreohelix nogalensis and Pupilla muscorum occur as Pleistocene fossils at lower elevations in the Sacramento Mountains than where they presently occur in the Sierra Blanca Mountains (in which there
and with sedimentary bedrock, greatest species diversity and
areno known fossiliferousdeposits).
Apart from the above differences, altitudinal distributional
concomitantly with decreasing elevations into the lower TransitionandtheUpperSonoranZones.A similardecreaseis shown alongtheigneoustransectsinprogressingupwardinto the Hudsonian Zone. In this regard, both highest and lowest elevations tend to be inhabited by hardy, ecologically eurytopic species, occurring through several thousands offeet in elevation.
patternsshow similarityinacomparisonoftheSierraBlanca
Peak and the two Sacramento Mountains transects (abbreviated
belowtoSB andSacM).GastrocoptaquadridensandPunctum minutissimum were restricted to the Canadian and Transition
ACKNOWLEDGMENTS
Zones,CionellalubricatotheTransitionandUpperSonoran DillonwishestothankDrs.A.H.Harris,D.V.LeMone,and
Zones,andGastrocoptapellucidatotheUpperSonoranZone in both the S B and S a c M transects.
R. A.Smarttfortheirhelpfulcommentsandcriticisms.He thanks Ramon Llavona for cartographic work done. He also acknowledges the assistance of the following: Rick Lockwood, Paul Mason, Bob Garretson, Mark Secord, Reg Blaylock, Holly Woelber,JonEnz,ChrisHarrison,KarstenGronert,andHwan Kim.Finally,butcertainlynotleast,heisdeeplygratefultohis wife, Loretta S. Dillon, for her continued support, patience, and
Six species extended from the Canadian Zone down to at least the uppermost part of the Upper Sonoran Zone in both groups of transects: Discus whitneyi, Euconulus fulvus, Hawaiia minuscula, Vertigogouldii, Vitrinapellucida, and Zonitoides arboreus. Very similar were altitudinal distributions ofsixotherspecies,exceptthat,inthese,specimenswere taken
encouragement.
tranSect.
I n s u m m a r y , it a p p e a r s t h a t i n m o u n t a i n s b o t h w i t h i g n e o u s
largest land-snail populations are to be found from the middle Transition to middle Canadian Zones. These values decrease
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